If you've ever been around this kind of failure investigation before, the question of examining all the in service units you "think" are fine to see if they really are does jump out at you. We'll see if a "deviant" condition discovered in the "believed good" APU battery from the ANA aircarft leads to that. I've Googled and find no evidence to suggest they've been down that path. Yet.
Not like taking all these batteries out of the fleet will keep these aircraft from going anywhere...
One issue with this is that some of these conditions--dendrites in particular--can be very hard to find. The act of looking tends to destroy the evidence that they were there in the first place.